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March 3, 1964 R; K. GOLDEN MAGNETIC CORE ANALOG TO DIGITAL CONVERTER Filed oct. 11, 19Go Q N n .N m N ollmz: l|| .lll 2N M I I I I l||- 1|||| M m a WIL l lll N W K. m |||||I ISN MM M W llll l||||||| m IIII Il l N R w IIIIIlLI N .0E 1111 ...l om |.I m ll N NN United States Patent O 3,123,817 MAGNETIC CORE ANAOG T DIGITAL CONVERTER Robert K. Golden, Peekskill, N.Y., assignor to International Easiness Machines Corporation, New York, N.Y., a corporation of New York Filed Oct. 11, 1960, Ser. No. 62,033 7 Claims. (Cl. 340-347) This invention relates to analog to digital conversion apparatus and more particularly to a converter having a plurality of switchable magnetic cores energizable to determine the successive binary digits of the number corresponding to the value of the analog input.

Many types of analog to digital converters are known and they yvary widely in speed, principles of operation and cost. Many converters use an electronic counter, a precision current or voltage control circuit for each counter denomination to generate a reference analog value and a very sensitive voltage comparing device to detect a difference between the reference analog and the input analog value. Others generate a plurality of regulated currents or voltages and by a plurality of comparing devices, subtract certain of these currents or voltages from the analog current or voltage to determine the binary digits of the digital number. The comparing devices and the vsubtracting circuits of this latter type are both expensive, delicate and quite subject to errors due to aging.

It has been determined that magnetic cores of the well known square hysteresis loop type are usable for both subtracting a binary digit value or values from an analog value and for indicating which is the larger, thus providing a comparing and subtracting function in one inexpensive `and reliable part. Allso the comparison function is based on lthe absolute difference of the quantities compared and does not change with the magnitude of the quantities nor does the effectiveness of a magnetic core change appreciably with time. As a further advantage, such cores require little power from the analog circuits and will operate at a speed suiicient for most applications.

IThe converter described herein utilizes one such magnetic core comparing circuit `for each denominational order of the binary number to be determined. Each core is initially biased by a flux proportional to the denominational value of its own and all denominations of higher order and an opposing iiux proportional to the analog value is then applied. An order by order comparison is then started with the highest denominational order and progressed to the successive lower orders. If, in the highest order, the analog value is greater than the binary denomination value, a corresponding binary denomination winding is kept energized on all lower order cores, otherwise the windings are deenergized. In each successive lower order, the resultant flux in the core, that is, the ilux due to the analog value less the flux due to the higher order binary denomination windings remaining energized, is tested to determine Whether the binary denomination windings corresponding to that order and on the lower order cores `are to be kept energized or are to be deenergized. After the iinal comparison in the lowest order core, the analog value is determined in binary terms and Will be indicated by the denomination circuits remaining energized.

It is then an object of this invention to provide an an- ICC alog to digital converter using magnetic cores together with simple and reliable electronic circuits.

It is also an object to prov-ide an analog to digital converter capable of high speed, accurate operations without moving parts, or expensive `and delicate components.

A further object of the invention is the provision of a sturdy, reliable converter using magnetic cores and stabile electronic components of the switching, on or ott', type.

A st-ill further object is the provision in a converter of magnetic core comparing circuits to determine the digits of the binary number equal to the value of an analog quantity yapplied to the converter.

Another object is to develop a converter which requires a minimum of expensive regulating circuits to provide reference values.

The foregoing and other objects, features, and advantages of the invention -will be apparent from the following more particular description of a preferred embodiment of the invention, as illustrated in the accompanying drawings.

ln the drawings:

FIGURE l is a diagrammatic showing of the preferred embodiment of the invention; and

FIGURE 2 is a diagram showing the timing of energization of the circuits of FIGURE l.

As shown in FIGURE l, there are eight magnetic cores 10y to 17' provided, one for each binary order digit to be determined, although more or less cores may be `used as required for the precision desired. Each core is com posed of a well known high retentivity magnetic material such as magnetic iron oxide with a substantially square hysteresis loop. lt is characteristic of such cores that one magnetic orientation will be retained until application of Vat least a minimum flux tending to force an opposite orientation and the core will then switch rapidly to `said opposite orientation. Each core has a plurality of conductive windings which are energizable to induce ilux therein. One winding 18 on each core 16-17 is designated as a sense lwinding to indicate when its core switches from one to another direction of magnetic orientation. Each sense winding 18 is shown with one end grounded and Iwill give a positive voltage pulse at the other winding end when the core changes orientation from a first to a second direction and `a negative pulse at said other winding end when the orientation changes from lthe second to the rst state. Also each core 10 to 1'7" has a winding 2bl which is energized to provide a flux proportional to the `analog value to be converted into binary form. It should be noted that each core is magnetically independent of the other cores and therefore the llux due to the analog windings need not lbe the `same in all cores. It is necessary only that the iluxes generated in any core by consistent with each other but any desired flux ratio may be used between the cores.

Each of the cores l@ to 17 also has a reference winding 21 thereon to induce a reference ilux in each core itl to 17 which iiux is opposed to the llux generated by the analog winding Ztl. In each core iti to 17' the ux due to winding 21 is made substantially proportional to the value of the binary denomination of the core. That is, in core 17, the flux due to winding 21 will be proportional to 27 as compared to the analog value, in core 16 the flux from winding 21 will be proportional to 25, for core 15, the tlux is proportional to 25 etc. until for core 10, the flux from winding 2l is proportional to 2G. In

areaal? of FEGURE l, the windings 2l are shown in series so that the same current ilows in each winding, which requires that the number of turns in the winding 2l for a core be proportional to the digital value associated with the core l) to 17, thus winding 2l for core ll7 would require E23 timos as many turns as winding 21 for core lll. rl'his may be impractical for small cores and the larger binary denominational values and, as an alternative, winf ings 2l may be separated into two or more circuits having different currents therein, the sole essential being that the :flux induced in each core it) to l? by windings 2i be proportional to the value of the denominational order of the core.

lt will be noted trat in FGURE l, the flux Value indicated for each winding 2l has a minus sign as a superscri This is to indicate that the induced by the winding is s'uiliciently less than the exact binary value to enable the core l@ to .i7 to be switched to the opposite magnetization by an exact analog value. Considering, for example, core 27, winding 2l is tirst energized to switch the core to one magnetic state and winding 2t? is then energized. if the ilux due to winding 2l were exactly proportional to 27 and the analog value to be read were exactly 27, the liuxes due to windings 2i) and 2l would just neutralize each other and the core 17 would remain in the set state. When, however, the ilux from winding 2l is less than the denominational value by the amount of flux needed to switch the core i7, the unneutralized iluX from winding 2d when the analog value is exactly 27 will be enough to switch core 17 to the opposite state. if the provision of slightly less ilux than is required for the exact denominational value introduces complications due to fractional winding turns or current regulation, windings 2l may be energized to provide the exact digital flux required and the switching flux may be provided for the cores lll to 117 by a separate bias winding whose flux aids that oi winding 21. In eiect, this amounts to an otlset in the comparing point of a core and it will be recognized that the more abruptly a core switches from one state to the other, the sharper will be the dis -notion between adjacent analog values.

Cores it? to lo are also provided with a winding 22 which is retained energized if the analog value being converted is equal to or greater than 27. rl`he ilux from winding 22 opposes that of analog winding 20 and for each core is proportional to 27, in eilect subtracting that value from the analog value. Similarly, each of the cores itl to l has a winding 25 which will be retained energized if the binary equivalent of the analog value has a 26 term and will, in eilect, subtract 26 from the analog value. Cores lll to i4 have another winding 26 which is kept energized it the binary equivalent has a term, cores lil to i3 have a winding 27 which will stay energized it the equivalent binary number has a 24 term. Also cores l@ to lip have a winding 2S for the 23 term, cores l@ and lll have a winding 3@ for the 22 term and core lll has a winding 3l for the 21 term. ln each case, only the fluxes produced by the windings 22, 25, 26, 27, 28, 3d

and 3l are of concern and the number oif winding turns and the current through them can be varied inversely as desired to produce a satisfactory winding arrangement. As noted above with respect to windings 2l, the series arrangement oi the binary digit windings 22, 25, 26, 27, 28, and 3@ is not essential and other well known arrangements to induce the required fluxes in cores l@ to lo may be used as desired.

Each of the cores ll to i7 has associated therewith a control circuit to determine it the associated binary digit winding for all lower cores shall be retained energized. Each control circuit comprises a trigger 3d which is reset to one of its two stable states at the start of a conversion cycle by a pulse on the common line 35 connected to the reset terminals oi all triggers 3d. Each trigger 3dhas a set terminal which when energized by an appropriate signal will set the trigger to the other of its stable states and each set terminal is connected to tne free end of the sense winding i8 on its associated core lll to i7. The triggers 34 are polarity sensitive and are so connected to winding i3 that the voltage pulse from a winding lil when the core is switched from the initial state by the current through analog winding 29, will be effective to set the associated trigger 34 whereas the setting of the core to the initial state by windings 2l, 22, 25, 26, 28, 3?, and 3l will have no eiect on the trigger 34.

When a trigger 34 is set, a control voltage is present on its output line 37 and this voltage may be conducted to output terminals and to indicators Each output terminal represents one binary order of the equivalent binary number and the combination of energized and unenergized output terminals will represent the full equivalent binary number. Each output line '37 is also connected to one input of a conventional OR gate 39 which will give an output signal when any input is energized. The other input of OR gate 39 is connected to a control voltage to be later described. The output of OR gate 39 is connected to a gate or switch lil to enable ilow oi current from a source el of regulated current through the windings 22, 25, 26, 27, 2S, 3@ or 3l for 'the binary order corresponding to the controlling core lll to i7. The sensing winding l for core llt) is connected to a trigger 3d similar to the other triggers Eli but since there is no core of a lower order or a winding corresponding to the 20 binary order, the output of associated trigger 34 is used for indicating the digit value only.

When it is desired to convert an analog value into digital form, the sequence of operations is as indicated in the timing diagram of FIGURE 2 which has an arbitrary time base. This sequence may be controlled by any suitable equipment as cam operated switches, electronic switches or similar devices and the rst step is the closure of a switch 42 to apply a reset voltage to common line 35 to pull all triggers 34 into their reset state. Immediately after this at time l, switches 43 to 5t) are closed to apply control voltage to all OR gataes 39 to activate gates 4t) and to complete the circuit through windings 21. Activation of gates 4t) will connect the current sources 41 to energize all windings 22, 25, 26, 27, 2S, 30 and 31. Such energization will set all cores 1l) to 17 into an initial state. After any transients generated have dissipated, the reset voltage on line 35 is removed to free triggers 34 for operation to the set state. The output lines 37 or triggers 34 are at a non-controlling Voltage at this time but the gates 4t) pass current because OR gates 39 have theirl outputs held at a control voltage by the inputs through switches 43 to 49.

The analog circuit is next completed through windings 20 by closure of switch 5l at time 2, and depending upon the analog value, the flux due to windings 2d may switch one, or two, or more of the cores starting with core l'. When any core is switched to the opposite state, the voltage pulse induced in winding 18 will switch the connected trigger 34 to its set state causing a control voltage to appear on its output line 37. Shortly thereafter at time 4, switch 43 is opened and its control voltage is removed from OR gate 39 for core 17. If the trigger 34 for core i7 has been set, its line 37 is at the control voltage and the output of its OR gate 39 continues at the control level to maintain activation of gate lll and retain the energizeion of the 27 windings 22 on cores 1G to i6. lf, however, the core 17 did not switch its state, this indicates that the analog value is less than 27, trigger 34 for core 17 is not set and when the switch 43 is opened, all control voltage is removed from OR gate 39. The output of the OR gate 39 then goes to the ineiective level and its gate 4i) halts the ilow of current through windings 22.

It the analog value is greater than 27 plus 26, it will have caused both cores i7 and lo to switch state and the triggers for cores lo and i7 will both have been set when the analog circuit was completed at time 2. lr", however, the analog value is 26 or more but less than 27, core i7 does not switch and when switch 43 is opened, the current through winding 22 of core 16 disappears. This leaves only the iiux through Winding 21 to oppose the ilux due to the analog current in winding 20 and in the assumed case, this is not suicient to hold core 16 in the initial state. Core 16 will therefore switch from its initial state when switch 45 is opened and will set its trigger 34 to maintain current flow through its gate 40 and the 26 windings 25 on cores 10 to 15 after switch 44 for its OR gate 39 is opened at time 5. Where the analog value is less than 26 or is more than 27 but less than 27 plus 26, the initial flux from winding 20 or the resultant tlux if the 27 winding 22 is energized, is insufficient to overcome the 26 flux from coil 21 and switch core 16 from its initial state so that trigger 34 for core 16 is not set. Therefore, when control Voltage is removed from its OR gate 39 by opening of switch 44 at time 5, the current through the 26 coils 25 stops which may permit cores 15, 15 and 14, 15, 14, and 13 or a like group to switch from their initial state and set their triggers 34.

There are four ranges of analog values which will cause core 15 to switch from its initial state and set its trigger 34 to maintain current through the 25 windings 26. When the analog value is 27 plus 26 plus 25 or more, core 15 will switch at time 2 when the analog current starts in winding 20. lf the analog value is 26 plus 25 or more but less than 27, core 15 will switch when switch 43 opens to deenergize winding 22. For the other two cases, when the analog value is at least 25 but less than 26 or at least 27 plus 25 and less than 27 plus 26, core 15 will switch when the current through the winding 25 stops as switch 44 opens. For other values of the analog, core 15 will not switch and the 25 current through windings 26 will cease as switch 45 opens at time 6.

The operation for the lower order cores to 14 is substantially similar to the above description for cores 15, 16, and 17 in that each core will switch to the opposite state if the analog value iux is greater than the effective binary value iluX selected by the set cores of higher denominational order plus the denominational value flux set by winding 21. Setting of any core from its initial state will set its trigger 34 to maintain a current tlow through its gate 40 and the windings of like denominational value on all lower order cores. The switches 43, 44 49 for cores 17, 16 11 are opened successively starting at time 4 so that each core can be set successively going from core 17 to core 10. The initial reference current through windings 21 is not removed until a new analog conversion cycle is started. After all switches 43 to 49 are opened, the triggers 34 which are set will show by their activated indicators 3S which binary orders have a signiiicant digit therein and these indications may be utilized in any desired manner.

As a specific example, assume that the analog value t0 be converted is 11100000. When analog current passes through windings 20 at time 2, the resulting flux will be suicient to switch cores 17, 16, and from their initial setting and will set their three triggers 34 to prevent interruption of the current through windings 22, 25, and 26 for all lower order cores. ln each lower order core 10-14, the flux from windings 22, 25, and 26 plus that from winding 21 will be greater than the ilux from the analog winding and none or" these cores will be switched. Therefore, after switch 49 opens at time 10, the only triggers set are those for the cores 17, 16 and 15 and the indicators 33 of these triggers will indicate the correct binary value 11100000.

As a second example, assume that the analog value'is 01101011. The flux due to this analog value is less than the 27 flux in core 17 from the current in winding 21 and the uX induced in cores 10 to 16 by winding 22 so that none of the cores 10 to 17 will be switched when the analog current is passed through winding 20 at time 2. Trigger 34 for core 17 will not have been set and the current through windings 22 will stop when switch 43 is opened at time 4. Now core 16 will have an analog flux of a value of 1101011 which is greater than the flux from winding 21 which has a value of 1000000 and core 16 will switch to set its trigger 34. Also, core 15 will switch at this time since its analog flux has a value of 1101011 which is greater than the ux of 1100000 from windings 21 and 25. When the switches 44 and 45 separately open, there is no change in the current flow as the set triggers for cores 16 and 15 maintain current liow in windings 25 and 26. Core 14 cannot Switch in this conversion cycle for the analog iluX value 1101011 is less than the iuX value of 1110000 impressed by windings 21, 25, and 26 and therefore when switch 46 opens at time 7, the current through the 24 windings 27 ceases and core 13 will switch since its analog flux value of 1101011 is more than the flux value of 1101000 'rom coils 21, 25, and 26. Switching of core 13 will maintain current through the 23 windings 2S after switch 47 opens at time S. 1n core 12 the lux value from windings 21, 25, 26, and 23 is 1101100 which is more than the analog flux value so that core 12 does not switch state and the current through windings 30 stops when switch 48 opens at time 9. ln both remaining cores 10 and 11, the anaiog iiux has a greater value than the ilux Values of 1101010 and 1101011 impressed on these cores by the energized windings so the triggers 34 for these cores will be set. ln the case of core 10, it will be noted that the opposing flux is indicated to be equal to that due to the analog value but, as above noted, the effect of the windings 21 is suciently reduced to allow switching to take place under this equality condition so that trigger 34 for coil 10 will be set. The indicators 38 for triggers 34 now indicate the digital binary value of 01101011 for the analog input.

ln general as will be seen from the above, each core is initially subjected to a ilux approximately equal to its denominational value and to the sum of the denominational values of the higher denominations and also to an opposing iiux proportional to the analog value to be converted. lf the analog vaine is the greater, the core is switched from its initial state and a ilux proportional to the denominational value of the core remains subtracted from the analog flux in each lower order core. lf the analog iiux is the lesser, no switching occurs and the flux proportional to the denominational value of the core is removed from the lower order cores. In either case, the next lower order core then will be switched if the resulting ux is less than the value assigned to the core. if any core does not switch from its initial magnetic state, the current producing a flux proportional to the denominational value of that core in all lower order cores will be stopped during the conversion cycle and the iower order cores will then be subjected to a different iiux resultant which may or may not cause some cores to switch as determined by the impressed analog value. After the lowest denominational order core has compared the remaining analog value flux less the flux proportional to the determined higher order binary digits to determine the lowest order digit, the outputs of the triggers which were set when the cores switched may be tested to indicate the converted analog value.

It may be noted that the above description has been set out with the implied assumption that the analog value remains constant during the interval required for conversion and this will generally be true where the compcnents used in this converter are electronic and operate in a conversion cycle of from to 100 microseconds. For very rapidly varying analog values, it will be desirable to provide a holding circuit to maintain a constant analog input during the conversion.

While the invention has been particularly shown and described with reference to a preferred embodiment thereof, it will be understood by those skilled in the art that the foregoing and other changes in form and details areaal? may be made therein without departing from the spirit and scope of the invention.

What is claimed is:

-1. In a converter for determining a digital binary number equivalent to an analog value, a plurality of cores, each core switchable from one magnetic state to another and each representing one denominational order of a binary number, means to generate in each core a lluX substantially proportional to the sum of the values of the denominational orders represented by said core and all cores of higher denominational order whereby said plurality of cores will be set to said one magnetic state, means to apply to each core an opposing llux proportional to said analog value and tending to switch said cores to said other state, llux control means to stepwise reduce the generated flux in each of said cores to a flux not substantially less than the flux proportional to the value of the denominational order represented by Said core, the first step of flux reduction being proportional to the value of the highest denominational order represented and effective in all lower order cores, each succeeding step being equal to one-half of the amount f the immediately prior step and effective in successively fewer lower order cores, and means controlled by any core when switched to said other state by said opposing uX to control said linx control means to prevent, in all lower order cores, the lluX reduction step proportional to the denominational value or" the core switched.

2. In a converter for` determining a binary number equivalent to an analog value, a plurality of cores switchable from one magnetic state to another, each core representing one binary denominational order, a winding on each core to generate a llux proportional to the analog value to be converted, a second winding on each core to generate an opposing llnX substantially proportional to the value of the denominational order represented by the core, means to generate in each core an additional opposing linx proportional to the sum of the higher denominational orders, control means to first apply said opposing lluxes to said cores to set said cores to said one magnetic state, to thereafter enable energization of said analog windings and to thereafter stepwise deactivate said generating means to reduce said additional opposing flux by successive steps, the lirst step being proportional to the value of the highest denominational order and each succeeding step being of one-half of the value of the immediately prior step, and means controlled by each switched core to maintain, in all cores of lower denominational order, an opposing linx proportional to the denominational value of the core switched.

3. In a converter to determine a digital binary number equivalent to an analog value, a plurality of cores switchable from one magnetic state to another and each representative of one denominational order of said binary number, means to produce in each core a flux substantially proportional to the value of the denomination represented by said core, a plurality of second means, one associated with each core except the core representing the lowest denominational order, to produce in all cores of lower denominational order an additional lluX proportional to the value of the denomination of the associated core, means to apply to each core an opposing lluX proportional to said analog value, switching means to first energize said first and second llux producing means to set said cores into said one magnetic state, to then energize said opposing linx applying means to tend to reset said cores to said other magnetic state and to thereafter deactivate said plurality of second means seriatim starting with the one associated with the core representing the highest denominational order, and an output device for each core, each output device being settable by its core when the core is switched to its other magnetic state and acting when set to prevent deactivation of the one of said plurality of second means which is associated with its core, the set output devices repred senting the significant digits ot the equivalent binary number.

4. ln a converter to determine a digital binary number equivalent to an analog value, a plurality of cores, one for each denominational order of said binary number and each switchable from one magnetic state to another, a first winding on each core energizable to produce in each core, a llux substantially proportional to the value of the denominational order of said core, a second winding on each core to produce an opposing ux therein proportional to said analog value, one additional winding on each core other than the core of highest denominational order for each core of higher denominational order, means to energize said first windings and said additional windings to set said cores to said one magnetic state and to then energize said second windings to tend to switch said cores to said other state, sequentially operating switches to deenergize said additional windings starting with those related to the core of highest denomination order and means including a sense winding on each core and a trigger circuit set when said core is switched to said other state to maintain energization oi the windings related to said core on the cores of lowerV denominational order.

5. ln a converter to determine a digital binary number equivalent to an analog value, a plurality of cores switchable from one magnetic state to another, each denominational order of said binary number being represented by one of said cores, a winding on each core to induce a llux therein substantially proportional to the value of the denominational order of said core, a second winding on each core to induce therein an opposing ilux proportional to the analog value, a sense winding on each core and a trigger connected thereto to be set when said core is switched to said other state, a current source for each core other than the core of lowest `denomination and a winding energizable by each current source on each core of lower denominational order, a plurality of switch means cyclically operated to first energize said rst windings and said current source energizable windings to set said cores to said one magnetic state, to secondly energize said second windings to tend to reset said cores to said other state and thirdly to deenergize said current source energizable windings seriatim starting with the windings energized by the current source for the highest denominational order core and a gate controlled by each set trigger other than that of the lowest denomination core to maintain energization of the windings connected to the Vcurrent source for its core.

6. In a converter to determine a binary digital number equivalent to an analog value, a core for each denomination of said number, each core being switchable from one magnetic state to another, a first winding on each core to induce therein a llux substantially proportional to the value of the denomination of said core, a second winding on each core to induce therein an opposing llux proportional to said analog value, a sense winding on each core, a plurality of triggers, one connected to each sense winding to be set to a control state when the sense winding connected thereto generates a pulse to indicate tliatrits core has switched to said other state, a denominational current source for each core other than the core of lowest denomination, a winding energizable on each core o lower denomination by each current source to induce in said lower denomination cores a linx proportional to the value of the denomination of the current source, a gate for each current source, each gate activatable to control energization by its current source of the windings energizable thereby, switches to rstly energize said lirst windings and to activate said gates to enable energization of all said current source windings whereby said cores will be set to said one magnetic state, to secondly enable energization of said second windings to tend to set said cores to said other state, and to thirdly deactivate said gates seriatim startthe represented denominational order of the equivalent binary number contains a signicant digit.

References Cited in the le of this patent UNITED STATES PATENTS Buser Nov. 29, 1960 

1. IN A CONVERTER FOR DETERMINING A DIGITAL BINARY NUMBER EQUIVALENT TO AN ANALOG VALUE, A PLURALITY OF CORES, EACH CORE SWITCHABLE FROM ONE MAGNETIC STATE TO ANOTHER AND EACH REPRESENTING ONE DENOMINATIONAL ORDER OF A BINARY NUMBER, MEANS TO GENERATE IN EACH CORE A FLUX SUBSTANTIALLY PROPORTIONAL TO THE SUM OF THE VALUES OF THE DENOMINATIONAL ORDERS REPRESENTED BY SAID CORE AND ALL CORES OF HIGHER DENOMINATIONAL ORDER WHEREBY SAID PLURALITY OF CORES WILL BE SET TO SAID ONE MAGNETIC STATE, MEANS TO APPLY TO EACH CORE AN OPPOSING FLUX PROPORTIONAL TO SAID ANALOG VALUE AND TENDING TO SWITCH SAID CORES TO SAID OTHER STATE, FLUX CONTROL MEANS TO STEPWISE REDUCE THE GENERATED FLUX IN EACH OF SAID CORES TO A FLUX NOT SUBSTANTIALLY LESS THAN THE FLUX PROPORTIONAL TO THE VALUE OF THE DENOMINATIONAL ORDER REPRESENTED BY SAID CORE, THE FIRST STEP OF FLUX REDUCTION BEING PROPORTIONAL TO THE VALUE OF THE HIGHEST DENOMINATIONAL ORDER REPRESENTED AND EFFECTIVE IN ALL LOWER ORDER CORES, EACH SUCCEEDING STEP BEING EQUAL TO ONE-HALF OF THE AMOUNT OF THE IMMEDIATELY PRIOR STEP AND EFFECTIVE IN SUCCESSIVELY FEWER LOWER ORDER CORES, AND MEANS CONTROLLED BY ANY CORE WHEN SWITCHED TO SAID OTHER STATE BY SAID OPPOSING FLUX TO CONTROL SAID FLUX CONTROL MEANS TO PREVENT, IN ALL LOWER ORDER CORES, THE FLUX REDUCTION STEP PROPORTIONAL TO THE DENOMINATIONAL VALUE OF THE CORE SWITCHED. 